The use of transparent conductive oxide (TCO) films on glass is known in the art. Such TCO films on glass are typically deposited pyrolitically (via pyrolysis) which requires expensive equipment and processing (i.e., large capital investments).
The process of making float glass is known in the art. For example, see U.S. Pat. Nos. 3,954,432, 3,083,551, and 3,220,816, the disclosures of all of which are hereby incorporated herein by reference. Generally speaking, the process of making float glass involves delivering molten glass to a pool of molten tin (which forms a so-called tin bath) in a forming chamber. Shortly after the initial delivery, the applied tractive forces in withdrawing the glass from the forming chamber attenuate the glass while it is cooling to form a continuous sheet of a ribbon of glass of a desired, predetermined, shape and thickness which is continuously advanced over the bath of molten tin. Pyrolytic coatings are typically applied to the upper surface of the glass after it exits the tin bath, on the non-tin-bath side of the glass.
It will be appreciated that there exists a need in the art for a method of forming TCO films which is less costly than known pyrolysis techniques.
In certain example embodiments of this invention, a TCO film is integrally formed along with the float glass during the float glass manufacturing process. In certain example embodiments of this invention, a compound including donor properties in respect to tin oxide (e.g., antimony and/or an oxide thereof) is added to the glass batch for the melt stage of the glass manufacturing process. The hot glass ribbon with the donor therein proceeds onto the tin bath during the “float” process. A thin tin oxide inclusive film forms in the glass at the side of the glass having the interface with the tin bath during the float process (i.e., at the bottom surface of the hot glass ribbon which lays on the tin bath). The donor diffuses into the tin oxide inclusive film that is integrally formed at the glass surface which interfaces with the tin bath, thereby changing the electrical properties of this tin oxide inclusive film/layer (e.g., increases the number of electrons, thus increasing conductivity) causing the tin oxide inclusive layer to be a transparent conductive oxide (TCO) film or layer integrally formed with the float glass. In particular, the donor element(s) diffuses into the tin oxide inclusive layer area of the glass thereby increasing the number of electrons therein, which results in a higher conductivity of the layer.
Float glass made in such a manner so as to include a TCO film integrally formed therein can be used in applications such as solar cells, oven doors, defrosting windows, or the like in certain example embodiments of this invention.
In certain example embodiments of this invention, the donor material may be Sb (antimony) and/or Sb2O3 as a dopant for the tin oxide inclusive layer integrally formed with the float glass. However, other donor dopants may instead or additionally be used. The antimony will dope the naturally formed SnOx (e.g., 0≦x≦1) on the tin side of the glass, thereby producing a transparent conductive oxide film at this side of the float glass. Thus, an economical way has been found to produce a TCO layer at the tin side of the float glass by adding an amount of antimony and/or other dopant to the batch during the process of manufacturing the glass. In certain example embodiments of this invention, an example Sb and/or Sb2O3 dopant may make up from about 0.01 to 10% by weight of the glass batch and/or final glass, more preferably from about 0.1 to 5%, and most preferably from about 1 to 5%.
In certain example embodiments of this invention, there is provided a method of making float glass, the method comprising: providing a glass batch including soda, lime, silica and antimony; causing molten glass from the batch to be provided on a top surface of a tin bath, thereby causing a tin oxide inclusive film to be formed at the glass surface adjacent the tin bath; and wherein the presence of antimony increases the number of electrons in the tin oxide inclusive film formed at the glass surface so as to result in the formation of a transparent conductive oxide film at the glass surface that was adjacent the tin bath.
In other example embodiments of this invention, there is provided a method of making float glass, the method comprising: melting a glass batch including SiO2, Na2O, CaO and at least one electron donor; and locating a hot ribbon from the glass batch on a tin bath, so that a tin oxide inclusive layer is formed, and electrons are donated to the tin oxide inclusive layer by the donor, so as to provide a transparent conductive oxide film at a tin side of resulting float glass.
In still further example embodiments of this invention, there is provided float glass comprising: SiO2 67-75%, Na2O 10-20%, CaO 5-15%, wherein a transparent conductive oxide film is integrally formed with the float glass at a tin side thereof. The conductive oxide film may be formed with the help of at least one donor added to the glass batch.